The long-term objective of this project is to identify a new class of antibiotics targeting an underexploited pathway essential for the viability of all Gram-negative bacteria, the methylerythritol phosphate (MEP) pathway. Gram-negative bacteria are responsible for more than half of hospital acquired (nosocomial) infections which cost an estimated $5 billion dollars per year with >60% caused by resistant bacteria. The overuse of many antibiotics has resulted in a concurrent rise in resistance to dangerous levels. Future generations of existing antibiotic classes are expected to have shorter periods of utility than an entirely new class as bacteria will not have been subjected to selective pressure leading to resistance. The MEP pathway for isoprenoid biosynthesis represents a novel target for developing a class of antibiotic with greater potential for increased utility over existing antibiotic classes. Isoprenoid biosynthesis is an essential process of all living organisms. Isoprenoids represent one of the most diverse classes of natural products with a multitude of structural features and ranging in size from the ten-carbon monoterpenes to natural rubber with a molecular weight as high as 1.5 million. Despite this diversity, all isoprenoids are synthesized from two five-carbon precursors: isopententyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP). Two unrelated pathways for the biogenesis of IPP and DMAPP are found in nature. The mevalonate (MVA) pathway is found in humans, some Gram-positive bacteria and the cytosol of plants, while the MEP pathway is utilized by all Gram-negative bacteria, some Gram-positives and plant plastids. This natural distribution and a dearth of agents specifically targeting the MEP pathway make it an ideal new target for antibacterials. Only one compound targeting the MEP pathway has undergone clinical evaluation, therefore, any new chemical entity targeting this pathway represents an entirely new class of antibiotics. Echelon will utilize a novel, proprietary whole-cell screening platform to identify chemical agents that specifically target the MEP pathway. This will be accomplished by: First, developing biochemical tools for characterizing MEP-specific inhibitors (e.g. determination of MIC, IC50, enzyme target). Second, adapting a validated screening platform to allow for the identification of inhibitors against every step in the pathway. Third, screening chemically diverse libraries for MEP pathway inhibitors. Fourth, characterizing the inhibition observed as a result of hits. Fifth, synthesizing focused libraries of compounds around the scaffolds identified in the screen resulting in a molecule(s) with increased potency. Sixth, screening hits obtained in initial screens for the ability to kill Gram-negative bacteria responsible for nosocomial infections. Bacterial resistance to current antibiotics continues to increase in both hospital and community settings. The goal of this project is to identify novel antibiotics targeting a unique, underexploited pathway. Since there has been no selective pressure for bacteria to become resistant to these antibiotics, it is expected that compounds identified in this project will have a longer duration of utility than subsequent generations of the current antibiotics.